This invention relates generally to material handling equipment, and more particularly to a telescoping bridge crane system particularly arranged to be mounted over a floor of a structure, e.g., in the interior of the body of a truck, to provide maximum headroom between it and the floor of the structure.
Various bridge crane systems and devices are commercially available for use in over-the-road vehicles, such as trailer bodies, vans, trucks, and the like to enable the vehicle to be loaded and unloaded. For example, some devices and systems make use top running bridges mounted within the trailer adjacent the ceiling. In order to extend out of the trailer such bridges make use of hinged runways which are arranged to be held within a stowed position within the interior of the trailer body, and then to fold out of the rear of the trailer so that a portion extends beyond the end of the trailer to facilitate the loading and unloading of the trailer. This approach limits the storage space within the trailer in order to maintain clearance for the movement of the folding runway. It also requires a set-up procedure before the system is ready for use.
So-called “enclosed track” bridge crane systems solve the problem of load-lifting coverage beyond the runway and bridge envelope by utilizing telescoping bridges or runways each formed of an elongated hollow track section. In particular, at least one enclosed track is mounted horizontally at an elevated position and includes at least one wheel truck or trolley arranged to roll therein. The truck(s)/trolley(s) serve to suspend another enclosed track horizontally below the upper track. The lower enclosed track can be extended longitudinally with respect to the upper enclosed track, i.e., the truck(s)/trolley(s) can be rolled along the upper track from a stowed or a retracted position within the upper track to an extended position (also within the upper track but closer to its rear end). This action enables the lower track to be extended substantially beyond the rear end of the upper track section. A hoist or other lifting member can be mounted directly or indirectly on the lower track to enable the lifting of some load. Examples of such bridge crane systems are commercially available under the trademark MET-TRACK® Stand Alone Workstation Bridge Cranes from Spanco, a division of Transol Corporation, the assignee of the subject application.
While the use of upper and lower enclosed tracks requires no additional set-up, it nevertheless also results in the loss of valuable headroom, particularly if the system is utilized in a confined space, such as within a trailer or other hollow vehicle body. Moreover, such telescoping or runways must be located directly below the fixed (upper) track or runway to prevent moment loading on the truck(s)/trolleys supporting the lower track or runway, since such trucks/trolleys are not typically amenable for supporting moment loads.
Examples of other types of prior art devices and systems for enabling a vehicle body to be loaded and unloaded are also found in U.S. Pat. Nos. 4,360,307 (Larsson), 4,425,071 (Dunbar), 5,062,760 (Samaniego), 5,338,147 (Kucharczyk et al.), 5,743,702 (Gunderson), and 6,126,379 (Feldman et al.).
While the aforementioned prior art devices and systems may be suitable for their intended purposes they never the less leave much to be desired from one or more standpoints, e.g., taking up considerable headroom in the interior of the vehicle, complexity, cost, ease of operation, ability to handle loads extending substantially beyond the bounds of the vehicle interior, etc.